In general the twisted pair only makes the packed 1500 bites for each packet. Most OSes dont bother to play with the ethernet headder and let that be set and handeled by the card (if I rembemer correctly) and the 1460 MTU is the packet size minus the 40 bit headder.

That is generaly the size for ethernet. I'm still trying to figure out why they decided on such a small size for the packet though. Propibaly because of the expence of memory way back when (before memory was measured in KB ).

If you want to take down a network try playing with a small packet size like about 500 bites and then start pinging places. hping is a great tool.. Very usefull for playing with packets. Also check out fragrouter (I dont have a url for that but I know you can find it on google).

OK, great xplanation guys thanks alot! But do your think that the MTU size works for me? I am running in a 10MBps LAN and connected thru a floor switch (actually is a hub coz some floors uses 100MBps but ours still 10Mbps), and connected to the backbone of ATM.